A California man is suing Microsoft, alledging that his Surface tablet did not provide the advertised amount of disk space. The 32G device has 16G of space for users, as the operating system uses the other 16G. The 64G Surface leaves 45G free for users. The case will turn on whether Microsoft has clearly explained to customers how much free space the Surface leaves for their use outside of the OS. How much disk space does your OS consume?

There is also some level of expectation, based on competing products...

Android tablets use about 1GB of space for the OS overhead, iOS tablets are fairly similar... The surface uses 16 times more space! You don't expect such a massive difference between products which target the same market, advertise a similar level of specification and cost roughly the same.